No abstract

Improving the productivity of cucumber (Cucumis sativus L.) plants subjected to combined salinity and heat stresses is a significant challenge, particularly in arid and semi-arid regions. Gianco F1 cucumbers were grafted onto five cucurbit rootstocks and, together with an ungrafted control, were grown in Egypt in a net house with saline soil during the summer season over two years. The vegetative growth, yield, quality, biochemical, and mineral composition traits were measured. Although many differences were observed among treatments, in general, the grafted plants had a performance better than or similar to that of the ungrafted plants, based on the different parameters measured. In particular, the cucumber plants grafted onto the Cucurbita maxima × C. moschata interspecific hybrid rootstocks VSS-61 F1 and Ferro had the highest early and total marketable yields. These two rootstocks consistently conferred higher vigor to the scion, which had lower flower abortion rates and higher chlorophyll contents. The fruit quality and N, P, and K composition in the leaves suffered few relevant changes as compared with the control. However, the leaves of the VSS-61 F1 had higher catalase activity, as well as proline and Se contents, while those of Ferro had higher Si content. This study reveals that the grafting of cucumber plants onto suitable rootstocks may mitigate the adverse effects caused by the combination of saline soil and heat stresses. This represents a significant improvement for cucumber cultivation in saline soil under high-temperature stress conditions in arid regions.

Silicon (Si) plays an important role in plant growth and development, but the uptake, accumulation in tissue, and beneficial effects of Si differ greatly between plant species. Net house experiments were conducted with Cucumis sativus L. 'Shabah F 1 ' in 2013 and repeated in 2014 to determine the effects of Si supplementation on yield, fruit quality, and chemical composition. Diatomite (86-89% SiO 2 ) was applied to cucumber plants three times at two-week intervals after two weeks from transplanting through either foliar spraying (50, 100, 200 mg/l or soil drenching in the root area (500, 1000 and 2000 mg/l). All treatments produced higher early and marketable fruit yield (number and weight) in both years. At all growth stages, application of Si significantly increased fruit firmness, but the effects of Si on total soluble solids varied depending on growth stage and concentration of Si. Significant differences among treatments for ascorbic acid content of cucumber fruits were found in 2013 but not 2014. Tissue analyses showed that Si-treated plants had more Si in the leaves and fruits (% dry wt.), and phosphorus and potassium (% dry wt.) in the leaves compared to untreated controls. We conclude that both foliar sprays and soil drenches of Si have the potential to increase cucumber yield and fruit quality in net house production.